Operation: SENTRY
by NCR Ranger
Summary: Though the Covenant is defeated, the UNSC still faces stubborn threats from every angle: not only from remnants of the alien alliance, but from the resurgent Insurrectionist movement. It will take some of the best of the UNSC fleet to face them down, and take them off the board once and for all
1. Chapter 1

2554

August 15th

Epsion Eridani System

Aboard Vindication-class Battleship ' _Cannae_ ' ( Named for the Battle of Cannae, won by Hannibal Barca in 216 BC, and considered one of the most brilliant victories in military history )

Leading Battle Group Carthage

Shipboard clock: 0800 hours

* * *

Five slipspace portals, each of them a swirling vortex of cyan blue and coal black, flashed into existence. Out of each of them slid a UNSC warship, smoothly transitioning into realspace.

A decade or so ago, they'd have done this in a pretty scattered and semi disorganized way, owing to how Human FTL drives were more _moderately functional_ than _ideal_, and quite a few rungs down the technological ladder from their Covenant adversaries. Back then, Human fleets usually didn't _arrive_ as fleets when they'd finished jumping to their destination; there was always a bit of forming up they had to do before they were fully ready to engage with the longer the jump meaning more unwanted drift. Even worse, with the Covenant, equipped with their flawless drives, not needing to do that, battles between the two sides gave the aliens an edge before the first shots had even been fired.

Then again, all that was _back then_. Humanity had come a long way, and they'd made good use of all the Covenant- and Forerunner, of course- technology they'd gotten their hands on during the 20+ years of fighting. With the conflict between the UNSC and Covenant over, the human navy could _finally_ begin to fully refit their whole fleet to bring them up to par with the ( ex ) Covenant's tech level.

There wouldn't be any more unfair fights with the Humans not having the better odds anymore. The Covenant may have been beaten, but there were splinter factions of them littered over the galaxy, and many of them were still demented enough to think that it was their " Holy Mission " to wipe out Humanity. On top of that, the Insurrectionists weren't done with grinding an axe against the UNSC, and previously suppressed groups of them were popping up all over again.

There was no shortage of enemies for the UNSC. Its ships needed every edge they could get to keep the colonies safe, and those edges had to be sharp.

The way the 5 ship battlegroup had gone from FTL to sub-light while still keeping themselves in formation was all the proof anyone could ask for. All of them were exactly where they'd been before they'd jumped, with only minor drift being detected by the onboard instruments.

The engine exhaust ports of each vessel began blazing white, as they throttled up their reactors. Not all the way up, of course- they weren't in contact _yet. _

Still, they were moving fast enough for now. The blast shields that covered the windows of the command decks of the various ships began to retract, giving their captains a look outside- because no matter how advanced a ships sensor suites were, there was no true substitute for actually _looking_ outside when you first arrived on a scene.

And the Epsilon Eridani System was definitely one that deserved to get a visual combing. The battlegroup had jumped right to the knife edge of the system's inner asteroid belt- a field of millions of rocks, most of them _at least_ the size of a ONI prowler, all tumbling and spinning around in one great big carpet. If you looked hard enough past the innumerable ( which was _not_ an exaggeration ) rocks, you could make out the rather faint glow of the system's sun. Of course, even that tended to get covered up at random moments whenever a large enough asteroid floated past and blocked out said glow- sometime for hours if it was one of the asteroids that was _battleship_ sized. There were quite a few of those too.

It was essentially a _perfect_ hiding place. That was the generally the first thought of UNSC naval officers upon seeing this place: anyone who didn't want to be found and who didn't like the UNSC enough to shoot at them would find plenty of places to hunker down here.

URF ( United Rebel Front ) Insurrectionists striking out this very asteroid field had caused plenty of problems for the UNSC, long before, during, and even after the Covenant. They didn't have the resources ( and backbone, many fleet officers stated ) to face the UNSC in open battles, so they employed the guerilla approach instead.

And of course, all guerilla armies need their hideouts.

None of that was lost on the commanding officer of the battlegroup:Captain Derek Jensen, clad in his ash-grey command uniform with its gold rank insignia, standing on the bridge of his command vessel, at the center of the UNSC ships, staring out at the field of rocks.

He stood straight and tall, all 6'0 ft of him. His eyes- which his wife Michelle had told him were the same color as the flare of a warship's sub-light engines- flicked back and forth, studying the field.

Of course, there were no_ windows_ for him to watch through. Windows were a structural weakness, after all. Instead, the bridge of a_ Vindication_-class was buried deep in the hull, beneath multiple layers of Titanium-A3 armor plating. It was taking a lesson from the Covenant, keeping the ship's nerve center so well protected.

Still, that didn't mean that anyone inside couldn't get a look outside. The bridge had a direct link to multiple high powered external cameras, all synced to provide real-time imagery of what was going on outside. Slaved to the bridge's panoramic screens, it created the feeling of actually having windows, without the vulnerability. The camera feed could also be routed to the central commander's dias, giving a tactically vital big picture way of viewing space.

For now, though, the big screens were enough.

Ajax wasn't looking for anything in particular; it was obvious you weren't going to find anything that was hiding out in this giant maze of rocks simply by looking at it. No, he was watching them because he actually found them somewhat pretty. There was something oddly mesmerizing about the sheer number of the things, and the way the ones that floated close to the external cameras that looked like they were spinning slowly, but he knew they absolutely were not.

_Alright. Enough gawking at the scenery. Do that on your own schedule when your next furlough comes up_

Shaking his shaved head a bit at his own indulging at the view, he turned back around to face the bridge's interior.

Which was a _big_ one, to boot.

Ajax had begun his career as the XO of a_ Paris_-class frigate, the '_ Yorktown's Eternal Glory ' ( _named for some battle fought on Earth centuries ago, evidently ). The bridge of that vessel had been a _third_ of the size of this one- at_ least. _Some aspects of it were the same ( the way that the workstations were set up so that you could either stand or sit at them ), while others were not ( the wraparound placement of the panoramic bridge windows ) but the overall space available was the biggest change, as in it was a lot less. You could throw a baseball across the bridge of a _Paris_-class, or most of it, anyway.

But, on a _Vindication_-class battleship ? You had to _shout_ to be heard on the other side of _its_ bridge. The entire space was spread out and open, with different levels that went further down the farther you went into the bridge. The skipper's station was near the back, complete with his/her own standing console, and a a padded command chair with arm rests. Heck, even the workstations for the lower ranking sailors working the place were nice to sit on too- though they weren't close by to the CO's position. Instead, they were arranged around in a rough horseshoe shape, placed so that everyone posted to them had a view of both the skipper, and the main access doors onto the bridge ( In the highly unlikely event of a boarding action, anyone breaching the bridge wouldn't have a clear shot into their backs ).

It was like stepping into the bridge of a Star Destroyer (according to by-now ancient movie series that had originated from Earth, called " Star Wars " ); packed wall to wall with technology, staffed by a platoon's worth of officers and sailors. There was so much room here, and it was so _busy_.

( Not that some of those working here didn't make time to shoot the breeze about random things, but that couldn't be controlled. Besides, making time was a valuable skill )

Ajax took that all in after a moment, as usual. Instantly while doing so, he noticed his XO- a was approaching: A tall ( though slightly shorter than Derek by about an inch or so ), stubble-chinned man named Jared Koasner.

" Seems we made a clean jump, sir ", greeted the ' _Cannae_ 's second in command. His strong South African accent carried easily over the ambient noise of the bridge, turning a head or two a few yards away.

In keeping with the way South Africans tended to have a lot of gravitas, whether because of their stature or accents ( or both ), Jared wasn't an exception. He was eye to eye with Derek in height, and built like an MMA fighter. The brawn didn't come without intelligence with him, though; the man was an able right hand to the captain of the _Cannae,_ reinforcing the chain of command and advising with alacrity and skill.

" Only 2 degrees off our projected arrival point. And they even managed to drop us on the _edge_ of the field, not _in_ it ", he continued.

" I noticed. Commendable work by Nav ", Derek agreed. " Upgraded FTL systems or not. We're in optimal position now. "

He turned away from the main viewport screen, and began heading back to the center of the bridge, with Jared keeping pace. Nearby crewmembers glanced up as they went by, and the standing ones momentarily stiffened respectfully.

" I do appreciate an organized battlegroup; makes forming ranks much easier. ". Derek stated. " Makes me wonder how the Battle of Alpha Augire would've turned out for poor Admiral Cole. Anyway, any news on the group perimeter ? "

" No contacts on any long range sensors. But if we get any, we'll be prepared. ", affirmed the_ Cannae'_s second.

He nodded slightly to make the point. " All those rocks out there have my attention. Could be someone lurking in there. Let them come. "

" Yes, Mr Koasner. As long as we don't cross the border from confidence to overconfidence. ", Derek noted.

" Overconfidence gets one killed. I know."

That was no bravado, Derek was aware. He knew his crew; they were not green, including Jared. Everybody on the battleship had been green once, but that was long ago. Most of them had cut their teeth fighting the Covenant, and many of the others had seen action against the splinter factions of the alien alliance that cropped up in the years after the conflict. What few green crewmembers there actually were had plenty of mentors to look up to. Ajax expected some of them to definitely need that superior experience.

Some of them, at least. They could always count on more experienced personnel.

They went by one of them right now, in fact: The ship's Chief weapons officer, Lt. Greg Hazrel., leaning over several of his subordinates at their weapons command cluster, closing working over the monitors.

" Lieutenant ! ", Derek greeted him.

Glancing up, and immediately recognizing who was speaking before he saw, the weapons officer promptly stood straight.

" Sirs 1 ", he replied crisply, nodding as well.

A moderately tall man- 5'10 was as high as he stood- Hazrel's mid length hair, boyish face, and close shaved facial stubble did a good job of hiding his fierce drive as a frontline combat officer, and his innate skill at managing the weapons systems of the_ Austerlitz_ like a conductor at an orchestra.

If there were any faults in him, it was probbably that he wasn't the kind of person who'd accept an impossible to win situation- like Kirk cheating at the Maru test. On one hand, it was commendable. On the other, it was unattainable. Still, points for giving it a go.

_Might not make a good caprain, but he works the guns like a pro_

_" _All green across the board ", Derek asked.

" Yes, sir. Sabers are unsheathed, so to speak. "

In other words, he was on point. Which was not surprising at all; Derek remembered how he'd timed a volley of Howler missiles to breach the hull of a URF frigate during the onset of Operation Ballista ( the follow up to the Anti-Insurrection Trebuchet ), cracking the ship in two like a drinking straw. It had been a masterful piece of work.

Dealing with URF and their ilk out in the open ( like back then ) was a different game than taking them on at their den, though. Still, Derek wasn't worried.

" Excellent. Keep me updated, Lieutenant. And keep your team on their toes. "

" Only way I run them, sir. "

With that, Derek and Jared continued on.

Derek liked meeting his officers, because he knew them. That was what helped the crew here to run like an oiled motorcycle.

He knew his ship, too; it was no mere corvette or prowler. It was a _Vindication_-class battleship, packing 3 spinal-mounted Mark IX MACs, as well as multiple batteries of Mark 2551 Onager Mass Drivers , Spitfire Coilguns, and Howler general purpose missiles.

On top of all the guns and high explosive missiles, the _Cannae _carried, as a special treat for the most deserving of its enemies, a variety of nuclear ordinance: HAVOK V-tipped missiles, Hyperion SBMs ( Space Ballistic Missiles ), and a handful of FENRIS-tipped missiles. Combined, they were enough to reduce half a planet the size of Earth to molten slag.

Basically, his ship was well covered in the firepower department. The white painted outlines of ships marked on the _Cannae'_s hull- ones the battleship had taken out in combat- was proof she was strong enough to take on anything any fighting force could throw against her.

( Of course, Derek personally believed God had been looking out for them all along too ).

Their conversation was interrupted at that moment by the appearance of the ship's AI: Tomoe. The glimmering avatar popped into view from the projector mounted at the commanders' station.

"_ Konichiwa, tono ( Hello, my master )_. ", she greeted Derek, offering a crisp bow.

The CO raised a brow, suppressing a smirk. This AI was one of those that'd been made to be as true to the source as could be-more or less.

More specifically, Tomoe here was named for Tomoe Gozen, a female Samurai of Fedual Japan, one of Earth's most revered warrior cultures. She was dressed much as the historical version of herself had been all those centuries ago: In plated, sharp sided armor, colored gold and red, with a white bandanna adorned with a centered blood red dot across her forehead. In one hand, she held a long handled weapon that resembled a curved sword mounted on the end of a pole, called a _Naginata. _Her dark hair was tied neatly back, with a strand or two hanging over the bandana's edge.

It was certainly impressive that UNSC software engineers could put such detail into their AI avatars: even Tomoe's face looked rather lifelike, aside from that it glowed, and shimmered. The avatar of the centuries-old-based warrior stood tall, looking like she was on some parade deck of a castle in Japan itself. She couldn't help ( obviously ) to be disciplined.

" Tomoe ", Derek nodded to her. " Glad you could join us. Anything to report ? "

" _Bango ( _No ), sir ". Tomoe didn't miss a chance to show off her bilingual abilities, and now was no exception. " No abnormalities on any system. Fleet telemetry indicates we are fully in formation. "

" Thank Nav ", Jared remarked.

" Indeed ", the Samurai concurred. " I told them so myself. Very diligent, they are. I also have ensured all weapon systems are fully primed, and prepared to have Lt. Hazrel remove their safeties. On your command, Captain, of course. "

Though it wasn't as if they were in imminent danger, Derek liked that they were always ready to react at a moment's notice. " Very good, Tomoe. Keep our scanning array active on that asteroid field; we'll be working our way along its perimeter as part of our patrol route. If there's any URF hiding there, they cannot be allowed to get off the first shot. "

" As you command ", Tomoe nodded again in acknowledgment. " I await further orders, sirs, if there are any. "

" Reduce engine power to 75 ", Jared instructed. " We shouldn't run at flank speed outside of contact. Prioritize scans for radiation flares. "

_Plasma from the Covenant, or WMDs from the URF. _Derek knew that Jared knew his craft.

At the Battle of Ballast, back in September of '52, it'd been Jared's focus on making sure that they were watching for radiation spikes against the vacuum of space debris had been a large reason why the Austerlitz hadn't received a volley of plasma bolts to her port side, courtesy of a CCS cruiser that thought it could hide itself.

Looking back, Derek was sure that would've been missed in the heat of the moment. He nearly had himself.

" One moment-done. "

_Show off. _

Now Derek stepped in : " Put a wing of Broadsword fighters on alert status. Arm 2 of them with HAVOK Vs. Authorization: KILLIMANJARO"

" Voice ID and codeword accepted ", Tomoe briefly sounded robotic, although still with that lilting Japanese accent. " HAVOC warheads online. "

She blinked, her subroutines finished with that task in a half second, and then looked to her superiors again:

" Done, tono. What would you have me do next ? "

" That's all for now, Tomoe. Maintain standing orders. Dismissed "

" Hai ( Yes ) ! "

With another bow, the Samurai vanished.

" Only a year old, you know. She grows up so fast. ", Derek commented.

" You know, she probably heard that ", reminded Jared.

" I wouldn't be surprised. "

Both of them took a few moments to survey the whole bridge again, watching everyone working their stations.

They looked ready, because they _were_ ready.

There was nothing to do now, but wait for contact.

That, and pray they weren't seen first.


	2. Can't slip the net

" All I need to know is: Did we get the drop on them ? "

The " them " in question were the result of the Cannae's stellar image-enhancement technology. What her long range sensors had detected was now displayed on the main bridge monitors as clearly as if they were cruising past within rock-tossing distance from the battleship's bow

Derek didn't take his gaze off the trio of blocky, gunmetal gray vessels that were clearly cargo haulers modded to carry missile pods that were displayed moving through the asteroids off the ' Cannae 's port bow.

Their engine ports weren't flaring the usual white-blue that was generally produced when a ship moved at high sublight speeds, and they were roughly maintaining a coherent formation. All of which were signs that they weren't aware the UNSC battle group had them locked in.

_Hopefully_. Any skipper worth his salt knew that getting in the first shot in space naval combat had been proven to decide the whole fight right then and there. Even if it didn't, it still gave you the high ground, tactically speaking.

" It appears we have, Captain. ". Shimmering her usual red hue, and with her Naginata clasped in one hand, Tomoe's avatar stood at the ready over her holoprojector at the bridge's command station. The atmosphere on the command deck was taking on an electric feel; everyone on it was keenly aware that contact was imminent.

" Our SIGINT Team reports no communications traffic between them as well. ", she added a moment later, canting her head to one side.

" Lt. Cmdr. Jovian said that herself, did she ? "

" Yes, Tono confirmed. " They are foolish enough to be communicating over open channels. "

Though Derek was obligated to manually check in with every section head on any new information they had, he didn't doubt either his AI or his SIGINT lead. Jovian was a highly perceptive and intuitive officer, who had a gift of streamlining and compelling all electronic intel into a ready made package, bow tied for immediate use. Her competence made Derek mildly concerned that ONI's Section One would attempt to steal her away for one of their " ops ".

Thank God they haven't pulled that stunt yet. ONI was worse than the Spanish Inquisition. Who would've thought that Catholics could be so pushy ?

" All hangar crews are reporting in ", Jared reported. " Longswords armed, and on alert status. "

" Excellent ". Derek nodded. " Deploy a screen of them now, but hold back the ones with the HAVOCs. Using ordance of that tier on a gaggle of freighters would be missallocation of valuable rescources. "

" I believe that's what Colonel Holland had to say about the deployment of Noble Team during the Battle of Reach, sir. "

" So he did. If they are indeed URF, then they'll require that kind of beatdown, and we'll give it to them. "

On the screens, the freighters in question were still following their course, ambling out of the way of the bulk of the asteroids in their immediate vicinity, on a track that was taking them further and futher into open space. It looked, at least from the battlegroup's angle, that they were sublighting their way out of the system.

They were playing it cool, so far. A clever move, Derek had to admit. If they were actually planning to run, or even if they _were_ planning to stay and fight, not running at flank speed right out of the gate was generally a good way to not draw attention to themselves.

_' Or preparing to jump '_

_' I do not want our prey to slip the hook '_

" Tomoe- get me a sensor scan on thier engine drives. I want to know if they're spinning up ", Derek instructed. " Quickly. "

" Hai ! "

As the AI's avatar winked out for a moment to do as she was told, Jared turned to address the CO. " Seems our engagement window might be closing, sir. "

" Could be. I don't plan to let it, tough. "

The brief exchange was interrupted by Tomoe's avatar reappearing. " Sir ! Long range sensor scane complete. Enemy vessel drives are not spooling . "

So, there was still a chance the URF flotilla could be run down. Derek mentally chalked that up as another point in the BG's favour.

_Finishing touches_

_" _In range for our MAC array ? ", he asked.

" Affirmative, sir. ". It was Jared who replied now, consulting his TACPAD, sycned with Tomoe's data.

" We're _that_ close ? " The URF vessels weren't that far off, relatively speaking. To the naked eye, they were specks, but that's how things were in space. Distances were staggeringly enormous, effortlessly eclipsing the ones found during terrestrial naval combat.

Despite his training and experience, Derek occasionally found himself surprised by the reach of naval weapons systems to reach out across these distances. It was annoying as sin- he wasn't a rookie, these things _shouldn't_ surprise him anymore-, but even so, here he was again. _Cannae'_s MAC array could touch those ships exactly where they were, even as far away as they were.

" 2,000k to contacts "

Said contacts lumbered on, still moving right to left.

" Maintain track ", Derek instructed.

Beneath his boots, he felt the deck shift slightly as _Cannae _re-positioned to keep the armed ships under the firing arc of her spinal mounted MACs. The travel time from their muzzles to their targets was the only real limiting factor in how long it took before they needed to adjust their sights, and with the distances and speeds involved, that wasn't short of a frame.

For now.

" Tome, are we in tightbeam range ? "

" Hai ", she replied, crisply as always. "

" Hail those vessels. " Derek crossed his arms. " Let's see if we can establish a signal with them. "

" So, we will attempt the tongue before we use the sword, sir ? ", the Samurai clarified philosophically,

Technically, that was the case, but on the other hand, there was more to it: Not _all_ armed vessels traipsing around were necessarily URF, or Insurrectionist. Granted, this deep into UNSC space, there wasn't much room for doubt, but even here, in the Inner Colonies, there were pockets of dissent and borderline sympathy for the Insurrectionist " cause ". Any one of them working with the rebels was guaranteed to be more beneath the radar than their counterparts out in Outer Colonies.

If they _were_ URF ( or any of their ragtag affiliates ), things would get loud real quick. That was fine, though. Everyone on the _Cannae_ was prepared, and the ship herself too.

" Handshake protocols initiated. ", Tomoe stated. " I will get the tea ready . "

" Ha, ha ", murmured Jared.

The AI avatar's constant shimmering changed for half second as she carried out the issued orders. On his command TACPAD, Derek brought up the menu of long range communications, waiting for a link to be ready. He didn't expect the possibly- Insurrectionists to be in a talking mood, and even if they were, this wasn't a negotiation. They were to heave to and prepare to be taken captive.

_Let's find out who's team you're playing for_

_" _Sir ? No response ", Tomoe reported.

Derek made a subtle 'hmmm ' noise at the back of his throat. " Send it again. Be sure to be loud and clear. "

He kept focused on his TACPAD, as another signal was sent out.

" Sir ! ", Jared exclaimed, though he sounded only mildly surprised. " They're altering course. "

" So they are, XO ", Derek noted.

His TACPAD had shown him the same thing. Frankly, he wasn't that surprised- Insurrectionists were known to pursure their goals with a stubbornness than ran the gamut from " highly committed " to " near Kamikaze ". They _knew_ they were being hailed by a UNSC battle group- ignoring them and making a run for open space for an FTL jump was clearly their chosen course of action.

It was one he planned to make cost them.

* * *

_Drrrm, drrm, drrrm !_

The electronic shrill of ' General Quarters ' blasted from every PA speaker aboard _Cannae, _from Deck One down to the lowest.

"** This is not a drill ! This is not a drill ! General Quarters ! General Quarters ! All hands man your battle stations !** "


End file.
